package day6;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int w = in.nextInt();
            int h = in.nextInt();
            int count = 0;
            int[][] array = new int[w][h];
            for (int i = 0; i < w; i++) {
                for (int j = 0; j < h; j++) {
                    array[i][j] = 1;
                }
            }
            for (int i = 0; i < w; i++) {
                for (int j = 0; j < h; j++) {
                    if (array[i][j] == 1) {
                        count++;
                        if (i + 2 < w) {
                            array[i + 2][j] = 0;
                        }
                        if (j + 2 < h) {
                            array[i][j + 2] = 0;
                        }
                    }
                }
            }

            System.out.println(count);
        }
    }
}
